The present invention relates to a method of supplying a chemical mechanical polishing liquid and an apparatus therefor.
Logic devices in the semiconductor devices are required to exhibit excellent high speed performances. In order to form multilevel interconnection structure, a process is necessary for carrying out a chemical mechanical polishing to a metal layer such as a tungsten layer, wherein an oxidizing agent is used for oxidizing the metal layer as a chemical polishing and subsequently removing the oxidized metal layer with polishing particles as a mechanical polishing. In order to rise the rate of the chemical and mechanical polishing, it is necessary to use an oxidizing agent as a solvent which has a large oxidizing capability.
The chemical mechanical polishing to the tungsten layer may be carried out by polishing agents. One of the available polishing agents which may, for example, comprise a mixing solution of hydrogen peroxide and iron nitrate as an oxidizing agent added with silica particles. Other available polishing agent comprises a polishing solution including KI03 as an oxidizing agent and alumina particles. Further another available polishing agent is an iron nitrate polishing solution showing a high polishing rate.
FIG. 1 is a schematic view illustrative of a conventional chemical mechanical polishing system, wherein an iron nitrate is used as a polishing liquid Iron Fe acts as a catalyst in the hydrogen peroxide solution for Fenton's oxidation to efficiently generate OH-radicals. Oxidizing power of the OH-radicals oxidizes tungsten to form WO.sub.4.sup.2- ions which promotes chemical etching to tungsten, resulting in an increase in rate of the chemical mechanical polishing.
Heavy metal such as Fe is added in small amount into the solvent for increasing the oxidizing power. However, such heavy metal is likely to reside on the polishing surface of the device. This residual heavy metal contaminates the device thereby deterioration in performances and characteristics of the contaminated device, whereby the reliability of the semiconductor device is lowered. In addition the residual heavy metal on the device also results in a further contamination of the as a cross contamination of the production line or manufacturing line. The cross contamination is extremely serious problem when the logic device is manufactured in the common production lime to DRAM which requires an extremely high cleaning level.
In the above circumstances, it had been required to develop a novel method of chemical mechanical polishing to a metal layer in surface of a semiconductor device free from the above problems.